A direct spin draw process is well known as one of the processes for obtaining polyester filaments similar to conventional filaments. Such a direct spin draw process is disclosed, for example, in Japanese Patent Publication No. 1932/1970. This process consists of quenching and solidifying melt-spun polyester filaments to their glass transition temperature or below, advancing the filaments in a heated zone, such as a hot tube, drawing them therein, applying to them an oil and taking them up through godet rollers. However, a defect of this direct spin draw process is that if the spinning speed (take-up speed at the first godet roller) is raised to a level as high as 4,500 m/min or higher to improve the productivity, the spun filaments are taken up in such a way that the strain in the filaments generated on drawing is not sufficiently relaxed and internal strain is therefore released after winding. This internal strain of the filaments causes deformation of the package.
The deformation of the package means, in practice, that both phenomena known as "bulge" and "saddle" become larger. In extreme cases, it is impossible to remove the package because the deformation causes a tightening of the paper tube of the package against its supporting spindle. Bulge is generated by relaxation of the internal strain of the filaments after take-up and the force thereby produced pressing the edge faces of the package. Saddle is generated by tightening of the central part where the hardness is comparatively low caused by the force generated by relaxation of the internal strain. Tightening of the paper tube caused by filament winding occurs when the press-tightening force is extremely large. Further, faults in the package occur during transportation.
As a process for solving the problems associated with the direct spin draw process, Japanese Patent Laid-Open No. 85020/1987 proposes a process wherein separate rollers are provided on each godet roller and the filaments are wound once or more onto these separate rollers and onto the godet rollers so that internal strain in the filaments is thereby relaxed.
Such a process for relaxation serves to extend the take-up time of the filaments between drawing and winding and thereby to relax the internal strain of the filaments. If the take-up time is extended in this manner, improvement of package uniformity can be certainly achieved to some extent, but this process is not always applicable to a wide variety of yarn deniers and the package is easily deformed when the filaments are as thin as 50 denier or thinner or the spinning velocity is 5,000 m/min or higher.
Moreover, when multiple filament yarns are formed in the direct spin draw process, each filament yarn tends to oscillate transversely and the paths of filament yarns become unstable or moving filament yarns interface each other. Such disadvantages as non-uniformity of filament quality and occurrence of yarn breakage thereby occur.